Abstract
In the hemopoietic system c-myb expression is required for proliferation of immature cells and its down-regulation is required for differentiation. In colonic mucosa c-myb expression occurs at levels comparable to immature hemopoietic cells. Inhibition of c-myb expression in colon cell lines, using anti-sense oligonucleotides, indicates that c-myb expression is required for proliferation. However, the mechanism of c-myb regulation during colon cell differentiation has not been explored. Using the LIM1215 and CaCo-2 colon carcinoma cell lines induced to differentiate with sodium butyrate, we demonstrate that c-myb mRNA is down-regulated as an early event in differentiation by a mechanism involving transcriptional attenuation in intron 1. By analogy with procaryotic and eucaryotic genes, transcriptional attenuation probably occurs in a region containing nineteen consecutive thymidine residues. Computer prediction of the secondary structure of the nascent mRNA chain encoded by this region suggests a strong potential for stem-loop formation. Sequence analysis of several colon tumour cell lines reveals mutations in this region that may disrupt transcriptional attenuation and result in the increased c-myb expression observed in colon tumours and tumour cell lines.
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Thompson, M., Flegg, R., Westin, E. et al. Microsatellite deletions in the c-myb transcriptional attenuator region associated with over-expression in colon tumour cell lines. Oncogene 14, 1715–1723 (1997). https://doi.org/10.1038/sj.onc.1201007
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DOI: https://doi.org/10.1038/sj.onc.1201007
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